#!/usr/bin/env python3
"""
PR Analyzer - Analyze PR complexity and suggest review approach.

Usage:
    python pr-analyzer.py [--diff-file FILE] [--stats]

    Or pipe diff directly:
    git diff main...HEAD | python pr-analyzer.py
"""

import sys
import re
import argparse
from collections import defaultdict
from dataclasses import dataclass
from typing import List, Dict, Optional


@dataclass
class FileStats:
    """Statistics for a single file."""
    filename: str
    additions: int = 0
    deletions: int = 0
    is_test: bool = False
    is_config: bool = False
    language: str = "unknown"


@dataclass
class PRAnalysis:
    """Complete PR analysis results."""
    total_files: int
    total_additions: int
    total_deletions: int
    files: List[FileStats]
    complexity_score: float
    size_category: str
    estimated_review_time: int
    risk_factors: List[str]
    suggestions: List[str]


def detect_language(filename: str) -> str:
    """Detect programming language from filename."""
    extensions = {
        '.py': 'Python',
        '.js': 'JavaScript',
        '.ts': 'TypeScript',
        '.tsx': 'TypeScript/React',
        '.jsx': 'JavaScript/React',
        '.rs': 'Rust',
        '.go': 'Go',
        '.c': 'C',
        '.h': 'C/C++',
        '.cpp': 'C++',
        '.hpp': 'C++',
        '.cc': 'C++',
        '.cxx': 'C++',
        '.hh': 'C++',
        '.hxx': 'C++',
        '.java': 'Java',
        '.rb': 'Ruby',
        '.sql': 'SQL',
        '.md': 'Markdown',
        '.json': 'JSON',
        '.yaml': 'YAML',
        '.yml': 'YAML',
        '.toml': 'TOML',
        '.css': 'CSS',
        '.scss': 'SCSS',
        '.html': 'HTML',
    }
    for ext, lang in extensions.items():
        if filename.endswith(ext):
            return lang
    return 'unknown'


def is_test_file(filename: str) -> bool:
    """Check if file is a test file."""
    test_patterns = [
        r'test_.*\.py$',
        r'.*_test\.py$',
        r'.*\.test\.(js|ts|tsx)$',
        r'.*\.spec\.(js|ts|tsx)$',
        r'tests?/',
        r'__tests__/',
    ]
    return any(re.search(p, filename) for p in test_patterns)


def is_config_file(filename: str) -> bool:
    """Check if file is a configuration file."""
    config_patterns = [
        r'\.env',
        r'config\.',
        r'\.json$',
        r'\.yaml$',
        r'\.yml$',
        r'\.toml$',
        r'Cargo\.toml$',
        r'package\.json$',
        r'tsconfig\.json$',
    ]
    return any(re.search(p, filename) for p in config_patterns)


def parse_diff(diff_content: str) -> List[FileStats]:
    """Parse git diff output and extract file statistics."""
    files = []
    current_file = None

    for line in diff_content.split('\n'):
        # New file header
        if line.startswith('diff --git'):
            if current_file:
                files.append(current_file)
            # Extract filename from "diff --git a/path b/path"
            match = re.search(r'b/(.+)$', line)
            if match:
                filename = match.group(1)
                current_file = FileStats(
                    filename=filename,
                    language=detect_language(filename),
                    is_test=is_test_file(filename),
                    is_config=is_config_file(filename),
                )
        elif current_file:
            if line.startswith('+') and not line.startswith('+++'):
                current_file.additions += 1
            elif line.startswith('-') and not line.startswith('---'):
                current_file.deletions += 1

    if current_file:
        files.append(current_file)

    return files


def calculate_complexity(files: List[FileStats]) -> float:
    """Calculate complexity score (0-1 scale)."""
    if not files:
        return 0.0

    total_changes = sum(f.additions + f.deletions for f in files)

    # Base complexity from size
    size_factor = min(total_changes / 1000, 1.0)

    # Factor for number of files
    file_factor = min(len(files) / 20, 1.0)

    # Factor for non-test code ratio
    test_lines = sum(f.additions + f.deletions for f in files if f.is_test)
    non_test_ratio = 1 - (test_lines / max(total_changes, 1))

    # Factor for language diversity
    languages = set(f.language for f in files if f.language != 'unknown')
    lang_factor = min(len(languages) / 5, 1.0)

    complexity = (
        size_factor * 0.4 +
        file_factor * 0.2 +
        non_test_ratio * 0.2 +
        lang_factor * 0.2
    )

    return round(complexity, 2)


def categorize_size(total_changes: int) -> str:
    """Categorize PR size."""
    if total_changes < 50:
        return "XS (Extra Small)"
    elif total_changes < 200:
        return "S (Small)"
    elif total_changes < 400:
        return "M (Medium)"
    elif total_changes < 800:
        return "L (Large)"
    else:
        return "XL (Extra Large) - Consider splitting"


def estimate_review_time(files: List[FileStats], complexity: float) -> int:
    """Estimate review time in minutes."""
    total_changes = sum(f.additions + f.deletions for f in files)

    # Base time: ~1 minute per 20 lines
    base_time = total_changes / 20

    # Adjust for complexity
    adjusted_time = base_time * (1 + complexity)

    # Minimum 5 minutes, maximum 120 minutes
    return max(5, min(120, int(adjusted_time)))


def identify_risk_factors(files: List[FileStats]) -> List[str]:
    """Identify potential risk factors in the PR."""
    risks = []

    total_changes = sum(f.additions + f.deletions for f in files)
    test_changes = sum(f.additions + f.deletions for f in files if f.is_test)

    # Large PR
    if total_changes > 400:
        risks.append("Large PR (>400 lines) - harder to review thoroughly")

    # No tests
    if test_changes == 0 and total_changes > 50:
        risks.append("No test changes - verify test coverage")

    # Low test ratio
    if total_changes > 100 and test_changes / max(total_changes, 1) < 0.2:
        risks.append("Low test ratio (<20%) - consider adding more tests")

    # Security-sensitive files
    security_patterns = ['.env', 'auth', 'security', 'password', 'token', 'secret']
    for f in files:
        if any(p in f.filename.lower() for p in security_patterns):
            risks.append(f"Security-sensitive file: {f.filename}")
            break

    # Database changes
    for f in files:
        if 'migration' in f.filename.lower() or f.language == 'SQL':
            risks.append("Database changes detected - review carefully")
            break

    # Config changes
    config_files = [f for f in files if f.is_config]
    if config_files:
        risks.append(f"Configuration changes in {len(config_files)} file(s)")

    return risks


def generate_suggestions(files: List[FileStats], complexity: float, risks: List[str]) -> List[str]:
    """Generate review suggestions."""
    suggestions = []

    total_changes = sum(f.additions + f.deletions for f in files)

    if total_changes > 800:
        suggestions.append("Consider splitting this PR into smaller, focused changes")

    if complexity > 0.7:
        suggestions.append("High complexity - allocate extra review time")
        suggestions.append("Consider pair reviewing for critical sections")

    if "No test changes" in str(risks):
        suggestions.append("Request test additions before approval")

    # Language-specific suggestions
    languages = set(f.language for f in files)
    if 'TypeScript' in languages or 'TypeScript/React' in languages:
        suggestions.append("Check for proper type usage (avoid 'any')")
    if 'Rust' in languages:
        suggestions.append("Check for unwrap() usage and error handling")
    if 'C' in languages or 'C++' in languages or 'C/C++' in languages:
        suggestions.append("Check for memory safety, bounds checks, and UB risks")
    if 'SQL' in languages:
        suggestions.append("Review for SQL injection and query performance")

    if not suggestions:
        suggestions.append("Standard review process should suffice")

    return suggestions


def analyze_pr(diff_content: str) -> PRAnalysis:
    """Perform complete PR analysis."""
    files = parse_diff(diff_content)

    total_additions = sum(f.additions for f in files)
    total_deletions = sum(f.deletions for f in files)
    total_changes = total_additions + total_deletions

    complexity = calculate_complexity(files)
    risks = identify_risk_factors(files)
    suggestions = generate_suggestions(files, complexity, risks)

    return PRAnalysis(
        total_files=len(files),
        total_additions=total_additions,
        total_deletions=total_deletions,
        files=files,
        complexity_score=complexity,
        size_category=categorize_size(total_changes),
        estimated_review_time=estimate_review_time(files, complexity),
        risk_factors=risks,
        suggestions=suggestions,
    )


def print_analysis(analysis: PRAnalysis, show_files: bool = False):
    """Print analysis results."""
    print("\n" + "=" * 60)
    print("PR ANALYSIS REPORT")
    print("=" * 60)

    print(f"\n📊 SUMMARY")
    print(f"   Files changed: {analysis.total_files}")
    print(f"   Additions: +{analysis.total_additions}")
    print(f"   Deletions: -{analysis.total_deletions}")
    print(f"   Total changes: {analysis.total_additions + analysis.total_deletions}")

    print(f"\n📏 SIZE: {analysis.size_category}")
    print(f"   Complexity score: {analysis.complexity_score}/1.0")
    print(f"   Estimated review time: ~{analysis.estimated_review_time} minutes")

    if analysis.risk_factors:
        print(f"\n⚠️  RISK FACTORS:")
        for risk in analysis.risk_factors:
            print(f"   • {risk}")

    print(f"\n💡 SUGGESTIONS:")
    for suggestion in analysis.suggestions:
        print(f"   • {suggestion}")

    if show_files:
        print(f"\n📁 FILES:")
        # Group by language
        by_lang: Dict[str, List[FileStats]] = defaultdict(list)
        for f in analysis.files:
            by_lang[f.language].append(f)

        for lang, lang_files in sorted(by_lang.items()):
            print(f"\n   [{lang}]")
            for f in lang_files:
                prefix = "🧪" if f.is_test else "⚙️" if f.is_config else "📄"
                print(f"   {prefix} {f.filename} (+{f.additions}/-{f.deletions})")

    print("\n" + "=" * 60)


def main():
    parser = argparse.ArgumentParser(description='Analyze PR complexity')
    parser.add_argument('--diff-file', '-f', help='Path to diff file')
    parser.add_argument('--stats', '-s', action='store_true', help='Show file details')
    args = parser.parse_args()

    # Read diff from file or stdin
    if args.diff_file:
        with open(args.diff_file, 'r') as f:
            diff_content = f.read()
    elif not sys.stdin.isatty():
        diff_content = sys.stdin.read()
    else:
        print("Usage: git diff main...HEAD | python pr-analyzer.py")
        print("       python pr-analyzer.py -f diff.txt")
        sys.exit(1)

    if not diff_content.strip():
        print("No diff content provided")
        sys.exit(1)

    analysis = analyze_pr(diff_content)
    print_analysis(analysis, show_files=args.stats)


if __name__ == '__main__':
    main()